The present invention relates to a high temperature resistant flotation core and to a high temperature resistant oil containment boom constructed therefrom which allows for the in-situ burning of spilled or leaked oil during offshore oil spill cleanup operations. In-situ burning represents one of the most effective means of eliminating large quantities of spilled oil. If conducted properly, with due consideration for the temporary reduction of air quality and the potential for exposure to fire, the in-situ burning of an oil spill can result in the least overall impact to the environment.
The remoteness of many oil exploration, production, and transportation activities (e.g., Alaska), combined with the nature of the environment, provides ideal conditions for in-situ combustion. When considered in conjunction with mechanical cleanup, chemical dispersants, and natural elimination processes, burning often provides an important option when some of the other techniques alone are impractical. For this reason, the oil industry in Alaska and in Canada has conducted numerous research efforts to identify the most efficient means of burning oil in place (Shell Oil Company et. al., 1983; S. L. Ross Environmental Research Limited, 1983).
Such research has revealed that oil can be ignited and combustion sustained when the oil layer on water is at least 1 to 2 mm thick. As thicknesses increase beyond this minimum value, there is less tendency for heat loss to the underlying water, and therefore the chances are greater for efficient combustion. Thick oil layers have been consistently burned with efficiencies in excess of 95%, even under artic conditions. To achieve such success through burning, it is important to concentrate any spilled oil as quickly as possible and to contain the burning oil so that winds and/or currents can help thicken the oil slick. During the burning process, temperature in the order of 1200.degree. C. is common.
Conventional oil containment booms are elongated cylinders having a generally circular cross-section. These booms float in water with approximately one-third of the boom submerged below the surface of the water forming a floating barrier to the spilled oil. The booms are typically stored in a roll on the deck of a ship and deployed downwind of a spill where it floats on the surface of the water and temporarily contains the spill.
U.S. Pat. No. 4,537,528 is directed to a fireproof boom core containing a flammable pollutant on a water surface, the boom comprising a flotation member of foamed polypropylene and at least two layers of heat-resistant, water-sorbent material surrounding the flotation member and extending into the water in the form of a depending skirt. The skirt functions to draw water up into the layers of heat-resistant material forming steam in the presence of flaming pollutant thereby allowing only the outer layer of heat-resistant material to become slightly singed. It is understood that a bottom-tensioned, cylindrical-flotation fire containment boom is manufactured by Fire Control Inc. utilizing the teachings of said patent. The boom consists of multiple layers of fire-resistant, wicking fabric positioned over steel canisters for flotation. An additional sacrificial layer and a coarse, wire-mesh barrier are used externally for abrasion resistance.
U.S. Pat. No. 4,619,553 discloses an oil boom system which utilizes a multilayered, fire-resistant blanket, and is manufactured by Minnesota Mining and Manufacturing Company (3M), the assignee of the present invention. The fire-resistant blanket is used as an add-on high temperature protective blanket to convert most conventional types of booms to a containment for burning oil. The blanket is placed about the periphery of the boom and is held in position by any number of fastening systems.
Another oil boom system provided by 3M is a high temperature oil containment boom which allows for the in-situ burning of spilled or leaked oil. The boom comprises an outer layer of polymer coated fabric, a first underlayer of high temperature resistant refractory fabric and a second underlayer of a high or intermediate temperature resistant refractory fabric which constrains and assists in retaining the integrity of a low density, high temperature resistant core. The layers are unified by sewing with high temperature resistant, ceramic thread or by mechanical fasteners.
Still another oil boom system provided by 3M is a redeployable high temperature resistant oil containment boom containing a cellular core. The oil containment boom comprises an outer layer of polymer coated fabric, a first underlayer of stainless steel mesh and a second underlayer of a high or intermediate temperature resistant refractory tight weave hybrid ceramic textile fabric, all of which surround and encase a cellular, high temperature resistant flotation core of inorganic spheres or granules contained and rolled in a stainless steel mesh. The layers are unified by sewing with high temperature resistant ceramic thread or mechanical fasteners.
Problems associated with the above mentioned fire containment oil booms are that they are either difficult to recover or are not reusable and some are not redeployable in the event it was found unnecessary to burn the oil. Furthermore, those which depend upon wicking to function often can plug because of contamination by silt or salt water. Even those which do not depend upon wicking to function, such as the latter mentioned boom which contained a cellular core, tended to lose as much as fifty percent of its buoyancy during use. These problems lead to less than desirable performance.